Chromium trifluoride

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Chromium trifluoride
Aluminium-trifluoride-3D-polyhedra.png
FeF3structure.jpg
Names
IUPAC name
Chromium(III) fluoride
Other names
Chromium trifluoride
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.029.216
PubChem CID
RTECS number GB6125000
Properties
CrF3
Molar mass 108.9913 g/mol (anhydrous)
163.037 g/mol (trihydrate)
181.05 g/mol (tetrahydrate)
Appearancegreen crystalline solid
Density 3.8 g/cm3 (anhydrous)
2.2 g/cm3 (trihydrate)
Melting point 1,100 °C (2,010 °F; 1,370 K)(sublimes)
negligible (anhydrous)
sparingly soluble (trihydrate)
Solubility insoluble in alcohols
soluble in HF, HCl
+4370.0·10−6 cm3/mol
Structure
Rhombohedral, hR24
R-3c, No. 167
Hazards
Lethal dose or concentration (LD, LC):
150 mg/kg (guinea pig, oral) [1]
US health exposure limits (NIOSH):
PEL (Permissible)
TWA 1 mg/m3 [2]
REL (Recommended)
TWA 0.5 mg/m3 [2]
IDLH (Immediate danger)
250 mg/m3 [2]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Chromium(III) fluoride is the name for the inorganic compounds with the chemical formula CrF3 as well as several related hydrates. The compound CrF3 is a green crystalline solid that is insoluble in common solvents, but the coloured hydrates [Cr(H2O)6]F3 and [Cr(H2O)6]F3•3H2O are soluble in water. The trihydrate is green, and the hexahydrate is violet. The anhydrous form sublimes at 1100–1200 °C. [3]

An inorganic compound is typically a chemical compound that lacks C-H bonds, that is, a compound that is not an organic compound, but the distinction is not defined or even of particular interest.

A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as parentheses, dashes, brackets, commas and plus (+) and minus (−) signs. These are limited to a single typographic line of symbols, which may include subscripts and superscripts. A chemical formula is not a chemical name, and it contains no words. Although a chemical formula may imply certain simple chemical structures, it is not the same as a full chemical structural formula. Chemical formulas can fully specify the structure of only the simplest of molecules and chemical substances, and are generally more limited in power than are chemical names and structural formulas.

In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was understood.

Contents

Structures

Like almost all compounds of chromium(III), these compounds feature octahedral Cr centres. In the anhydrous form, the six coordination sites are occupied by fluoride ligands that bridge to adjacent Cr centres. In the hydrates, some or all of the fluoride ligands are replaced by water. [4]

Octahedral molecular geometry

In chemistry, octahedral molecular geometry describes the shape of compounds with six atoms or groups of atoms or ligands symmetrically arranged around a central atom, defining the vertices of an octahedron. The octahedron has eight faces, hence the prefix octa. The octahedron is one of the Platonic solids, although octahedral molecules typically have an atom in their centre and no bonds between the ligand atoms. A perfect octahedron belongs to the point group Oh. Examples of octahedral compounds are sulfur hexafluoride SF6 and molybdenum hexacarbonyl Mo(CO)6. The term "octahedral" is used somewhat loosely by chemists, focusing on the geometry of the bonds to the central atom and not considering differences among the ligands themselves. For example, [Co(NH3)6]3+, which is not octahedral in the mathematical sense due to the orientation of the N-H bonds, is referred to as octahedral.

Ligand molecule or functional group that binds or can bind to the central atom in a coordination complex

In coordination chemistry, a ligand is an ion or molecule that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's electron pairs. The nature of metal–ligand bonding can range from covalent to ionic. Furthermore, the metal–ligand bond order can range from one to three. Ligands are viewed as Lewis bases, although rare cases are known to involve Lewis acidic "ligands".

Production

Chromium(III) fluoride is produced from the reaction of chromium(III) oxide and hydrofluoric acid: [5]

Chromium(III) oxide chemical compound

Chromium(III) oxide is the inorganic compound of the formula Cr
2O
3. It is one of the principal oxides of chromium and is used as a pigment. In nature, it occurs as the rare mineral eskolaite.

Hydrofluoric acid Solution of hydrogen fluoride in water

Hydrofluoric acid is a solution of hydrogen fluoride (HF) in water. It is a precursor to almost all fluorine compounds, including pharmaceuticals such as fluoxetine (Prozac), diverse materials such as PTFE (Teflon), and elemental fluorine itself. It is a colourless solution that is highly corrosive, capable of dissolving many materials, especially oxides. Its ability to dissolve glass has been known since the seventeenth century, even before Carl Wilhelm Scheele prepared it in large quantities in 1771. Because of its high reactivity toward glass and moderate reactivity toward many metals, hydrofluoric acid is usually stored in plastic containers.

Cr2O3 + 6 HF + 9 H2O → 2 [Cr(H2O)6]F3

The anhydrous form is produced from hydrogen fluoride and chromic chloride: [6]

Hydrogen fluoride chemical compound

Hydrogen fluoride is a chemical compound with the chemical formula HF. This colorless gas or liquid is the principal industrial source of fluorine, often as an aqueous solution called hydrofluoric acid. It is an important feedstock in the preparation of many important compounds including pharmaceuticals and polymers. HF is widely used in the petrochemical industry as a component of superacids. Hydrogen fluoride boils near room temperature, much higher than other hydrogen halides.

CrCl3 + 3 HF → CrF3 + 3 HCl

Another method of synthesis of CrF3 involves thermal decomposition of (NH3)CrF6: (NH4)3CrF6 → CrF3 + 3NH3 + 3HF A mixed valence Cr2F5 is also known. [7]

Uses

Chromium(III) fluoride finds some applications as a mordant in textiles and as a corrosion inhibitor. Chromium(III) fluoride catalyzes the fluorination of chlorocarbons by HF. [8] [9]

Mordant substance, usually a metal salt or oxide, used for setting dyes

A mordant or dye fixative is a substance used to set dyes on fabrics by forming a coordination complex with the dye, which then attaches to the fabric. It may be used for dyeing fabrics or for intensifying stains in cell or tissue preparations. As applied to textiles, mordants are mainly of historical interest because the use of mordant dyes was largely displaced by directs.

Related Research Articles

Europium(III) chloride chemical compound

Europium(III) chloride is an inorganic compound with the formula EuCl3. The anhydrous compound is a yellow solid. Being hygroscopic it rapidly absorbs water to form a white crystalline hexahydrate, EuCl3·6H2O, which is colourless. The compound is used in research.

Chromium(III) chloride chemical compound

Chromium(III) chloride (also called chromic chloride) describes any of several compounds of with the formula CrCl3 · xH2O, where x can be 0, 5, and 6. The anhydrous compound with the formula CrCl3 is a violet solid. The most common form of the trichloride is the dark green "hexahydrate", CrCl3 · 6H2O. Chromium chloride finds uses as catalysts and as precursors to dyes for wool.

Phosphorus trifluoride (formula PF3), is a colorless and odorless gas. It is highly toxic and reacts slowly with water. Its main use is as a ligand in metal complexes. As a ligand, it parallels carbon monoxide in metal carbonyls, and indeed its toxicity is due to its binding with the iron in blood hemoglobin in a similar way to carbon monoxide.

Iridium(III) chloride chemical compound

Iridium(III) chloride is the inorganic compound with the formula IrCl3. The anhydrous compound is relatively rare, but the related hydrate is useful for preparing other iridium compounds. The anhydrous salt is a dark green crystalline solid. More commonly encountered is the trihydrate IrCl3(H2O)3.

Bromine pentafluoride chemical compound

Bromine pentafluoride, BrF5, is an interhalogen compound and a fluoride of bromine. It is a strong fluorination reagent.

Cobalt(III) fluoride chemical compound

Cobalt(III) fluoride is the inorganic compound with the formula CoF
3. Hydrates are also known. The anhydrous compound is a hygroscopic brown solid. It is used to synthesize organofluorine compounds.

Iron(III) fluoride chemical compound

Iron(III) fluoride, also known as ferric fluoride, are inorganic compounds with the formula FeF3(H2O)x where x = 0 or 3. They are mainly of interest by researchers, unlike the related iron(III) chlorides. Anhydrous iron(III) fluoride is white, whereas the hydrated forms are light pink.

Ammonium bifluoride chemical compound

Ammonium hydrogen fluoride is the inorganic compound with the formula NH4HF2 or NH4F·HF. It is produced from ammonia and hydrogen fluoride. This colourless salt is a glass-etchant and an intermediate in a once-contemplated route to hydrofluoric acid.

Aluminium fluoride chemical compound

Aluminium fluoride (AlF3) is an inorganic compound used primarily in the production of aluminium. This colorless solid can be prepared synthetically but also occurs in nature as minerals rosenbergite and oskarssonite.

Vanadium(III) fluoride chemical compound

Vanadium(III) fluoride is the chemical compound with the formula VF3. This yellow-green, refractory solid is obtained in a two-step procedure from V2O3. Similar to other transition-metal fluorides (such as MnF2), it exhibits magnetic ordering at low temperatures (e.g. V2F6.4H2O orders below 12 K).

Gallium(III) fluoride chemical compound

Gallium(III) fluoride (GaF3) is a chemical compound. It is a white solid that melts under pressure above 1000 °C but sublimes around 950 °C. It has the FeF3 structure where the gallium atoms are 6-coordinate. GaF3 can be prepared by reacting F2 or HF with Ga2O3 or by thermal decomposition of (NH4)3GaF6. GaF3 is virtually insoluble in water. Solutions of GaF3 in HF can be evaporated to form the trihydrate, GaF3·3H2O, which on heating gives a hydrated form of GaF2(OH). Gallium(III) fluoride reacts with mineral acids to form hydrofluoric acid.

Antimony trifluoride is the inorganic compound with the formula SbF3. Sometimes called Swart's reagent, is one of two principal fluorides of antimony, the other being SbF5. It appears as a white solid. As well as some industrial applications, it is used as a reagent in inorganic and organofluorine chemistry.

Chromium(III) sulfate chemical compound

Chromium(III) sulfate usually refers to the inorganic compounds with the formula Cr2(SO4)3.x(H2O), where x can range from 0 to 18. Additionally, ill-defined but commercially important "basic chromium sulfates" are known. These salts are usually either violet or green solids that are soluble in water. It is commonly used in tanning leather.

Chromium(III) nitrate chemical compound

Chromium(III) nitrate describes several inorganic compounds consisting of chromium, nitrate and varying amounts of water. Most common is the dark violet hydrated solid, but an anhydrous green form is also known. Chromium(III) nitrate compounds are of a limited importance commercially, finding some applications in the dyeing industry. It is common in academic laboratories for the synthesis of chromium coordination complexes.

Arsenic trifluoride is a chemical compound of arsenic and fluorine with the chemical formula AsF3. It is a colorless liquid which reacts readily with water.

Bismuth trifluoride chemical compound

Bismuth(III) fluoride or bismuth trifluoride is a chemical compound of bismuth and fluorine. The chemical formula is BiF3. It is a grey-white powder melting at 649°C.

Chromium(II) sulfate chemical compound

Chromium(II) sulfate refers to inorganic compounds with the chemical formula CrSO4·n H2O. Several closely related hydrated salts are known. The pentahydrate is a blue solid that dissolves readily in water. Solutions of chromium(II) are easily oxidized by air to Cr(III) species. Solutions of Cr(II) are used as specialized reducing agents of value in organic synthesis.

Neodymium(III) fluoride is an inorganic chemical compound of neodymium and fluorine with the formula NdF3. It is a purplish pink colored solid with a high melting point. Like other lanthanide fluorides it is highly insoluble in water which allows it to be synthesised from aqueous neodymium nitrate via a reaction with hydrofluoric acid, from which it precipitates as a hydrate:

References

  1. ↑ "Chromium(III) compounds [as Cr(III)]". Immediately Dangerous to Life and Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  2. 1 2 3 "NIOSH Pocket Guide to Chemical Hazards #0141". National Institute for Occupational Safety and Health (NIOSH).
  3. ↑ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN   0-08-037941-9.
  4. ↑ F.H. Herbstein, M. Kapon and G.M. Reisner, "Crystal structures of chromium(III) fluoride trihydrate. Structural chemistry of hydrated transition metal fluorides. Thermal decomposition of chromium(III) fluoride nonhydrate" Zeitschrift für Kristallographie 1985, volume 171, pp. 209
  5. ↑ Gerd Anger, Jost Halstenberg, Klaus Hochgeschwender, Christoph Scherhag, Ulrich Korallus, Herbert Knopf, Peter Schmidt, Manfred Ohlinger, "Chromium Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005.doi : 10.1002/14356007.a07_067
  6. ↑ Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry of the Elements (2nd Edn.), Oxford:Butterworth-Heinemann. ISBN   0-7506-3365-4.
  7. ↑ Sturm. B.J. Phase Equilibria in the System Chromium(II)Fluoride-Chromium(III) Fluoride. Inorg. Chem., 1962, 1 (3), pp 665–672
  8. ↑ Mallikarjuna R. V. N.; Subramanian M. A. Fluoroolefin Manufacturing U.S. Patent 6,031,14, August 6, 1998; n.a.
  9. ↑ Ruh R. P.; Davis R. A. Proceess for Fluorinating Aliphatic Halohydrocarbons with a Chromium Fluoride catalyst and process for preparing the catalyst. U.S. Patent 2,745,886, May 15, 1956; n.a.
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